This invention relates to dental prophylaxis angles (commonly referred to as prophy angles). It has particular application to a low-cost prophy angle which need not be lubricated even after repeated autoclave cycles.
Most prophy angles currently available are either low-cost disposable prophy angles which are discarded after each use or else expensive reusable metal prophy angles which require a considerable amount of care to maintain. A reusable angle must not only be autoclaved between uses or procedures to ensure that the angle is sterile for the next procedure, but it must be maintained. Reusable angles need to be lubricated to run smoothly. The lubrication, however, breaks down and is lost over time through use and because of the autoclaving. Some manufacturers recommend that prophy angles be lubricated after every ten hours of use. If the angle is not lubricated, the angle will eventually seize up and become inoperable. Through use, debris may also find its way into the angle's head. This debris can interfere with the operation of the angle's gears, and can ultimately ruin the gears. Reusable angles must therefore be periodically disassembled for both cleaning and lubricating. Many dentists and hygienists do not lubricate and clean their prophy angles on a regular schedule. If the angles are not lubricated and cleaned periodically, they will eventually fail.
An example of an expensive, high-quality reusable prophy angle is the TS2.TM. angle sold by Young Dental Manufacturing Company of Earth City, Mo., the assignee of the present invention. This angle is shown as prior art in FIG. 1 and described in Bailey, U.S. Pat. No. 5,683,247, assigned to Young Dental Manufacturing Company. The disclosure of Bailey, U.S. Pat. No. 5,683,247 is incorporated herein by reference.
An early attempt to produce a lower-cost prophy angle was made by Young Dental Manufacturing Company around 1975, with a "Model C" reusable prophy angle. This angle used a two-piece body and head which were threaded together. A cap was press fit into the head. The driven gear of the angle included a bur tube but no lower stem. It was rotatably mounted entirely in the cap and sat on a flat shelf machined into the head. This design proved to be unacceptable commercially and was withdrawn from the market.
Bailey, U.S. Pat. No. 5,683,247 describes a relatively low-cost prophy angle which can be used for an extended period, on the order of a year or more, without maintenance. A commercial device made in accordance with that patent has been on sale under the mark CARE-FREE.RTM. by Young Dental Manufacturing Company for over two years and has been commercially successful. The cost of manufacturing the angle, however, has been higher than desired.
Another alternative to single-use disposable prophy angles and expensive reusable angles has been proposed in Wiseman, U.S. Pat. No. 3,163,934. That patent discloses a relatively low-cost prophy angle whose body, cap, and drive shaft bearing are made of polypropylene, and whose drive gear, driven gear, bearing-locking collar, and ball thrust bearing are made of metal. A small quantity of silicone lubricant is packed into the head (nose) of the angle. Although this angle is designed to be sealed and to be repeatedly sterilized, it is not sufficiently sealed to prevent intrusion of materials from the patient's mouth or leakage of lubricant during use, and it does not lend itself to repeated autoclaving. Moreover, its construction does not lend itself to precise alignment of the moving parts, thereby increasing the difficulty of making the instrument run smoothly, quietly, and reliably.